a) \(\dfrac{11}{21}+\dfrac{-4}{7}=\dfrac{11}{21}+\dfrac{-12}{21}=\dfrac{-1}{21}\)

b) \(\dfrac{5}{15}+\dfrac{14}{25}-\dfrac{12}{9}+\dfrac{2}{7}+\dfrac{11}{25}=\dfrac{1}{3}+\dfrac{14}{25}-\dfrac{4}{3}+\dfrac{2}{7}+\dfrac{11}{25}\)

\(=\left(\dfrac{1}{3}-\dfrac{4}{3}\right)+\left(\dfrac{14}{25}+\dfrac{11}{25}\right)+\dfrac{2}{7}=-1+1+\dfrac{2}{7}=\dfrac{2}{7}\)

c) \(\dfrac{2}{3}+\dfrac{5}{7}-\dfrac{3}{14}=\dfrac{28}{42}+\dfrac{30}{42}-\dfrac{9}{42}=\dfrac{49}{42}=\dfrac{7}{6}\)

d) \(\dfrac{2}{5}-\dfrac{3}{7}+\dfrac{9}{45}=\dfrac{2}{5}-\dfrac{3}{7}+\dfrac{1}{5}=\dfrac{14}{35}-\dfrac{15}{35}+\dfrac{7}{35}=\dfrac{6}{35}\)

e) \(\dfrac{21}{47}+\dfrac{9}{45}+\dfrac{26}{47}+\dfrac{45}{5}=\dfrac{21}{47}+\dfrac{1}{5}+\dfrac{26}{47}+\dfrac{45}{5}=\left(\dfrac{21}{47}+\dfrac{26}{47}\right)+\left(\dfrac{1}{5}+\dfrac{45}{5}\right)\)

\(=1+\dfrac{46}{5}=\dfrac{51}{5}\)

f) \(\dfrac{15}{12}-\dfrac{18}{13}+\dfrac{5}{13}-\dfrac{3}{12}=\left(\dfrac{15}{12}-\dfrac{3}{12}\right)+\left(-\dfrac{18}{13}+\dfrac{5}{13}\right)=1+\left(-1\right)=0\)

g) \(\dfrac{-8}{18}-\dfrac{15}{27}=\dfrac{-4}{9}-\dfrac{5}{9}=\dfrac{-9}{9}=-1\)

h)\(\dfrac{3}{7}+\dfrac{-5}{2}-\dfrac{3}{5}=\dfrac{30}{70}+\dfrac{-175}{70}-\dfrac{42}{70}=\dfrac{-187}{70}\)

i) \(\left(\dfrac{11}{12}:\dfrac{33}{16}\right).\dfrac{3}{5}=\dfrac{11}{12}.\dfrac{16}{33}.\dfrac{3}{5}=\dfrac{11.16.3}{12.33.5}=\dfrac{4}{15}\)

a)86.5 - 13.5 + (3 : 3).25

= 86.5² - 13.5² + 3³.5²

= 5²(86 - 13 + 27)

= 25.100 = 2500

b)28.76 + 44.28 - 28.20

= 28(76 + 44 - 20)

= 28.100 = 2800

c)-|-33| + (-12) + 18 + |45 - 40| - 57

= -33 - 12 +18 + 5 - 57

= -79

d)-500 - {5[409 - (2 . 3 - 21)² ] + 10} : (-15)

= -500 - {5[409 - 9] + 10} : (-15)

= -500 - {2000 + 10} : (-15)

= -500 - (-134) = -366

thank you bạn nha

a) x + 15 = 36 - 2x

x + 15 = 36 - (x + x )

15 =36 - ( x + x) - x

15 = 36 - x - x - x

15 = 36 - 3x

3x = 36 - 15

3x = 21

x = 21 : 3

=> x = 7

b) (x - 7) - (2x +5) = -14

x - 7 -( 2x + 5) = -14

x - (2x + 5) = -14 + 7 = -7

x - 2x - 5 = -7

x - 2x = -7 + 5 = -2

x - x + x = 2

x = 2 (-x + x cũng bằng chính nó)

=> x = 2

c) (x - 12) - 15 = (-7 + 20) - (18+x)

(x - 12) - 15 = 13 - (18 + x)

(x - 12) - 15 = 13 - 18 - x

(x - 12) - 15 = -5 - x

15 = (x - 12 ) - (-5 - x)

15 = x - 12 + 5 + x

15 = x + (-12) + 5 + x

15 = 2x + [(-12) + 5]

15 = 2x + -7

2x = -7 + 15

2x = 8

x = 8 : 2

=> x = 4

..................

\(a,70-5\times\left(x-3\right)=45\)

\(5\times\left(x-3\right)=70-45\)

\(5\times\left(x-3\right)=25\)

\(x-3=25:5\)

x - 3 = 5

x = 5 + 3 = 8

vậy x = 8

\(b,12+\left(5+x\right)=20\)

12 + 5 + x = 20

17 + x = 20

x = 20 - 17 = 3

vậy x = 3

c, 130 - (100 + x) = 25

130 - 100 - x = 25

30 - x = 25

x = 30 - 25 = 5

vậy x = 5

\(g,10+2\times x=4^5:4^3\)

\(10+2\times x=4^2\)

\(10+2\times x=16\)

\(2\times x=16-10\)

\(2\times x=6\)

x = 6 : 2 = 3

vậy x = 3

h, \(14\times x+54=82\)

\(14\times x=82-54\)

\(14\times x=28\)

\(x=28:14=2\)

vậy x = 2

\(k,15\times x-133=17\)

\(15\times x=17+133\)

\(15\times x=150\)

\(x=150:15=10\)

vậy x = 10

\(a,70-5\times\left(x-3\right)=45\)

\(5\times\left(x-3\right)=70-45\)

\(5\times\left(x-3\right)=25\)

\(x-3=25:5\)

x - 3 = 5

x = 5 + 3 = 8

vậy x = 8

\(b,12+\left(5+x\right)=20\)

12 + 5 + x = 20

17 + x = 20

x = 20 - 17 = 3

vậy x = 3

c, 130 - (100 + x) = 25

130 - 100 - x = 25

30 - x = 25

x = 30 - 25 = 5

vậy x = 5

\(g,10+2\times x=4^5:4^3\)

\(10+2\times x=4^2\)

\(10+2\times x=16\)

\(2\times x=16-10\)

\(2\times x=6\)

x = 6 : 2 = 3

vậy x = 3

h, \(14\times x+54=82\)

\(14\times x=82-54\)

\(14\times x=28\)

\(x=28:14=2\)

vậy x = 2

\(k,15\times x-133=17\)

\(15\times x=17+133\)

\(15\times x=150\)

\(x=150:15=10\)

vậy x = 10

2: \(=234+29-80+52^3=140791\)

3: \(=45\cdot\left(3250-225\right)=45\cdot3025=136125\)

4: \(=\left[\left(192-3\right):3\right]^2=63^2=3969\)

a: \(=\dfrac{-28}{36}+\dfrac{15}{36}-\dfrac{26}{36}=\dfrac{-39}{36}=\dfrac{-13}{12}\)

b: \(=\dfrac{11}{9}\left(\dfrac{15}{4}-\dfrac{7}{4}-\dfrac{5}{4}\right)=\dfrac{11}{9}\cdot\dfrac{3}{4}=\dfrac{11}{12}\)

c: \(=15+\dfrac{9}{7}+6+\dfrac{2}{3}-5-\dfrac{5}{9}\)

\(=16+\dfrac{88}{63}=\dfrac{1096}{63}\)

d: \(=\dfrac{5}{6}-\dfrac{1}{3}+\dfrac{2}{18}\)

\(=\dfrac{15-6+2}{18}=\dfrac{11}{18}\)

A=7 B=1 OR =0 C=2 D=4.5.6

a: \(2^{x}\cdot4=128\)

=>\(2^{x}=\frac{128}{4}=32=2^5\)

=>x=5

b: \(x^{15}=x\)

=>\(x^{15}-x=0\)

=>\(x\left(x^{14}-1\right)=0\)

=>\(\left[\begin{array}{l}x=0\\ x^{14}-1=0\end{array}\right.\Rightarrow\left[\begin{array}{l}x=0\\ x^{14}=1\end{array}\right.\Rightarrow\left[\begin{array}{l}x=0\\ x=1\end{array}\right.\)

c: \(\left(2x+1\right)^3=125\)

=>\(\left(2x+1\right)^3=5^3\)

=>2x+1=5

=>2x=5-1=4

=>\(x=\frac42=2\)

d: \(\left(x-5\right)^4=\left(x-5\right)^6\)

=>\(\left(x-5\right)^6-\left(x-5\right)^4=0\)

=>\(\left(x-5\right)^4\cdot\left\lbrack\left(x-5\right)^2-1\right\rbrack=0\)

=>\(\left(x-5\right)^4\cdot\left(x-5-1\right)\left(x-5+1\right)=0\)

=>\(\left(x-5\right)^4\cdot\left(x-6\right)\left(x-4\right)=0\)

=>\(\left[\begin{array}{l}x-5=0\\ x-6=0\\ x-4=0\end{array}\right.\Rightarrow\left[\begin{array}{l}x=5\\ x=6\\ x=4\end{array}\right.\)

F=(9.75.21\(\dfrac{3}{7}\)+\(\dfrac{39}{4}\).18\(\dfrac{4}{7}\)).\(\dfrac{15}{78}\)

=(\(\dfrac{39}{4}\).21\(\dfrac{3}{7}\)+\(\dfrac{39}{4}\).18\(\dfrac{4}{7}\)).\(\dfrac{15}{78}\)

=[\(\dfrac{39}{4}\).(21\(\dfrac{3}{7}\)+18\(\dfrac{4}{7}\))].\(\dfrac{15}{78}\)

=[\(\dfrac{39}{4}\).(21+18)+(\(\dfrac{3}{7}\)+\(\dfrac{4}{7}\))].\(\dfrac{15}{78}\)

=[\(\dfrac{39}{4}\).(39+1)].\(\dfrac{15}{78}\)

=(\(\dfrac{39}{4}\).40).\(\dfrac{15}{78}\)

=390.\(\dfrac{15}{78}\)=75

\(B=71\dfrac{38}{45}-\left(43\dfrac{8}{45}-1\dfrac{17}{57}\right)\)

\(B=71\dfrac{38}{45}-43\dfrac{8}{45}-1\dfrac{17}{57}\)

\(B=28\dfrac{2}{3}-1\dfrac{17}{57}=27\dfrac{11}{57}\)

\(D=\left(19\dfrac{5}{8}:\dfrac{7}{12}-13\dfrac{1}{4}:\dfrac{7}{12}\right).\dfrac{4}{5}\)

\(D=\dfrac{12}{7}.\left(19\dfrac{5}{8}-13\dfrac{1}{4}\right).\dfrac{4}{5}\)

\(D=\dfrac{12}{7}.\dfrac{51}{8}.\dfrac{4}{5}=\dfrac{306}{35}\)

Câu còn lại làm tương tự!

Chúc bạn học tốt!!!

a: 2/9=4/18

1/3=6/18

5/18=5/18

b: 7/15=14/30

1/5=6/30

-5/6=-25/30

c: -21/56=-3/7

-3/16=-63/336

5/24=70/336

-21/56=-3/7=-144/336

d: \(\dfrac{-4}{7}=\dfrac{-36}{63}\)

8/9=56/63

\(-\dfrac{10}{21}=-\dfrac{30}{63}\)

e: 3/-20=-3/20=-9/60

-11/-30=11/30=22/60

7/15=28/60